Vacuum pump



F. HOLWECK VACUUM PUMP May 6 1924.

Filed May 11. 1922 2 Sheets-Sheet 1 I May 6 1924.

, 1,492,846 F. HOLWECK VACUUM PUMP Filed May 11 1922 2 Sheets-Sheet. 2

, and useful Improvements Patented ay 6, 1924.

FERNLA'ND HOLWECK, F PARIS, FRANCE, ASSIGNOR TO THE MULLARD RADIO VALVE COMPANY, LIMITED, OF LONDON, ENGLAND.

vacuum rumr.

Application filed May 11,1922. 'Serial No. 560,165.

To all whom it may concern:

Be it known that I, FERNAND HoLWEoK, a citizen of the French Republic, residing in Paris, France, have invented certain new in Vacuum Pumps, of which the following isa specificatio This invention is for improvements in or relating to vacuum pumps for producing very high vacua, of the type introduced by Gaede and known as molecular pumps.

.Gaede has proposed (see Annalen der Physik, vol. 41, p; 337) to use a cylindrical rotor mounted in a cylindrical stator which is provided on its internal surface with a spiral groove, the direction of rotation of the rotor being such that the gas which is being evacuated is caused to. travel longi tudinally of the pump along this groove to the outlet which communicates with the auxiliary vacuum pump. The present invention has for its object to provide an improved construction of pump provided withsuch. a spiral groove extending from the inlet to the outlet, whereby the efficiency is improved and the rate at which the required degree of vacuum can be produced is considerably increased.

According to this invention, a vacuum pump of the type described and formed with a spiral groove on one of the opposed faces of the stator and rotor extending from the inlet to the outlet, is characterised in that the cross-sectional area of the said groove diminishes progressively in passing along it from the inlet to the outlet.

According to another feature of this invention, the pump is constructed of cylindrical form having a cylindrical stator provided with an inlet intermediate of its ends, and with two spiral grooves of opposite pitch extending in opposite directions from the inlet towards the ends of the pump.-

In a modified construction of pump ac-v cording to'this invention, it may comprise aflat cylindrical stator casing and a discshaped rotor within it, and the tapered spiral groove or grooves are formed on any or all of the opposed inner faces of the stator and rotor.

According to another feature of this invention, the driving of the rotor of a vacuum pump as above described is effected by means of a magnetic rotor enclosed in the stator, or in an air-tight casing in communication with the interior of the stator, together with external means for imparting a rive magnetically 'to the said magnetic rotor.

In the accompanying drawings, which illustrate more or less diagrammatically some embodiments of this invention- Figure 1 is a central longitudinal section of a cylindrical pump;

. Figure 2 is an elevation in section on the line 22 of Figure 1;

Figure 3 is a central section of a flat discshaped pump, and

Figure 4: is a face view of the stator-casing, taken on the line 1-4= of Figure 3.

Like reference characters indicate like parts throughout'these drawings.

Referring first to Figures 1 and 2, the

pump comprises a hollow cylindrical stator-' casing 10 closed at its ends by means ofend plates 11. A pipe connection 12 communicates with the interior of the stator at' the middle of its length, and constitutes the connection whereby the vessel to be evacuated is connected to the pump, that is to say, the pipe 12 constitutes the inlet to the pump.

The curved internal surface of the stator is provided with two spiral grooves formed on it; these grooves are of opposite pitch,-

and they extend from the inlet pipe 12 to the ends of the stator. As illustrated these grooves are of substantially rectangular section, and an important feature according to this invention is that the cross-sectional area.

of each of the grooves diminishes progressively from the inlet end of the groove to the outlet end. This diminution in cross-section can be effected in various ways, as for example by diminishing the width, or the.

' forming the wall between adj acent convolu tions should have its face opposite the rotor suitably situated with respect to the rotor to enable the pum to operate in the well known manner; t at is to say there mustibe only a small clearance, say-of the order of .01 to .05 millimetres. The invention is not limited, however, to these articular dimen- I sions, since any other suitable dimensions may be used.- The two ends of the statorcaslng communicate with the outlet from this pump which is indicated at 15 in Figure 2, the pipe 15 openinginto a channel 16 extending longitudinally of the stator and communicating with the interior thereof at the two ends.

The rotor consists of a plain cylindrlcal member 17 mounted on a shaft 18 which is rotatable in ball-bearings 19 in the end plates 11 of the stator-casing. One of the bear ings, 19, is provided with a closed cover 20 which forms an air-tight joint, and the other bearing is provided with a suitably packed bushing 21 which provides an alrtight joint for a driving connection. 22, whereby a drive is imparted to the shaft 18 and the rotor. The bush 21 may be packed with thick grease or other material, for the purpose of making a tight joint with the member 22. V

In the modified construction illustrated in Figures 3 and 4:, the stator-casing 23 is of flat cylindrical form and a flat spiral groove 24 is formed on one of its internal faces. One end of the groove communicates with the inlet 25, and the outlet 26 to the auxil-' iary pump communicates with the other end of the groove. This groove 24 may be of any desired shaping and cross-section, and tapers, so as to get progressively smaller from the inlet to the outlet.

The rotor 27 is in the form of a flat .diso carried by a shaft .28 which rotates in ballbearings 29 in an extension 30 of the statorcasing.

It will be appreciated that the tapered spiral groove or grooves above-mentioned may be formed on either of the opposed faces of the stator and rotor, and in the case of the construction illustrated in Figures 3 and 4, the roove could be formed on both the internal flat faces of the stator,

so that both flat faces of the rotor are 0 erative; alternatively, the grooves could e formed on both flat sides of the rotor if so desired.

Figure 3 also illustrates a modified arrangement for driving the rotor, and it is to be understood that this arrangement could also be applied to the construction illus-, trated in Figure 1.

Referring to Figure 3, the stator-casing 23, 30 is provided at the open end of the part 30 with an air-tight cap 31 within which there is mounted a magnetic armature or rotor 32 which is secured on an extension of the rotor shaft 28' or is otherwise in driving engagement therewith. The casing 31 is of non-magnetic material, and the stator of an asynchronous motor 33 is arranged outside it to cooperate with the are either within the stator-casing or in free communication therewith, and this is of importance from manufacturing consid erations, since bearings of the ball or roller type can be arranged to run either without lubricant or without a continuous or even intermittent supply of lubricant, so that the air-tight construction of the stator-casing is much facilitated, and this is particularly the case when the magnetic drive illustrated in Figure 3 is also used. These constructions of pump can therefore be relied upon for contmuous service 1f so desired.

This invention, therefore, provides a pump which may be designated as commercial apparatus, as distinguished from a laboratory instrument, and furthermore, the invention is held to cover the combination of the improved vacuum pump hereinbefore described with any vessel or apparatus in which it is required, .to'maintain a high degree of vacuum, the pump then being permanently connected to the vessel or apparatus and set in operation when necessary.

What I claim as my invention and'desire to secure by Letters Patent is 1. In a vacuum pump of the character described, the combination of a cylindrical stator and a cylindrical rotor, mounted one in the other, one of which members has an inlet and an outlet and is formed with a spiral groove on its face opposed to the other member extending from the said inlet to the said outlet, the cross-sectional area of which groove diminishes progressively in passing along it from the inlet tothe outlet.

2. In a vacuum pump of the character described, the combination of a cylindrical stator and a cylindrical rotor mounted one in the other, one of which members has an inlet and two outlets, one on either side of the inlet, and is formed with two spiral In testimony whereof I aflix my signature. I

FERNAND I-I OLWEGK. 

